Setting Default System Theme

[moe]

When a new user is added to the system, by default they get the Bluecurve 
theme. How is this default changed to another theme?

I've tried the following files, which seemed pertinent, but they didn't do the 
trick:
/etc/gtk-2.0/gtkrc
/etc/skel/.gtkrc
/etc/gconf/schemas/desktop_gnome_interface.schemas
/etc/gconf/schemas/metacity.schemas
/usr/share/themes/Default/gtk/gtkrc

Where is it hiding? :)

Thanks,

-Jeff